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1074

Appendix VI.

x 100

(d)  Reduction of area per cent, will be obtained from

original area   - contracted area
original area

(e)  The Modulus  of Elasticity will be most easily ob-

tained from a large scale plotting of the elastic line.    If
the plotted points are not truly in line, the best straight
line must be drawn through them and
unit stress

E =

elastic load     original length
area         elastic extension

unit strain

and the result may be stated in both tons and pounds to the
square inch.

The preceding directions will be a guide also to tests in
compression, strain, and deflection. In compression of ductile
materials very little information can be obtained, however, beyond
the elastic limit, for the specimen merely flattens out, and does
not fracture.

Pp. jc?5 and 839.    Influence    of   Temperature   on

Strength.—The behaviour of steel as its temperature is increased

50

too'    zoo'   300'   4co"    soo'    600"
TEMPERflTURE.5

700'     <SOO'     9OO'      tOOO°    JlOO"
FAHRENHEIT

f^g. 954,  SJfr/esiqlk, of Steel aZ Hjuqh T&np&r\aXuT&s.

is peculiar, and is indicated by the diagram in Fig. 954. At first
the strength decreases slightly, but then steadily increases till it
reaches a considerable maximum at about 500° F., then decreases